Optically transmissive microembossed receptor media

ABSTRACT

A receptor medium with a sheet having an optically transmissive microembossed imaging surface as one major surface thereof. The receptor medium can receive jettable materials, which include inks, adhesives, biological fluids, chemical assay reagents, particulate dispersions, waxes, and combinations thereof. The microembossed medium unexpectedly solves such common inkjet printing problems as feathering, banding, and mudcracking in inkjet printing systems by controlling how an inkjet drop contacts and dries on an inkjet receptor medium and also Moire&#39; effects but also provides sufficient optical transmissivity to be useful as overhead transparency media, backlit signage, and the like. Clear lines of demarcation between adjoining colors of a pigmented inkjet image graphic can be obtained without creation of the Moire&#39; effects. Methods of making and using the inkjet receptor medium are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Divisional of U.S. patent application Ser.No. 09/583,294, filed May 31, 2000, now allowed; which is aContinuation-In-Part of U.S. patent application Ser. No. 09/324,094,filed Jun. 1, 1999, now abandoned, which is incorporated herein byreference.

FIELD OF INVENTION

[0002] This application relates to inkjet printing media to improveeffective drying times of the inkjet ink, improve abrasion resistance ofthe inkjet image after drying, and prevent visual defects caused by inkbeading, ink spreading, or mudcracking, resulting in improved printquality. More specifically, this application relates to microembossedtransparent ink jet receptor films which are suitable for use withdesktop ink jet printers for the production of presentation qualityoverhead transparencies. Moreover, this application relates to managingthe coalescence of ink within cavities of a microembossed receptormedia.

BACKGROUND OF INVENTION

[0003] Image graphics are omnipresent in modern life. Images and datathat warn, educate, entertain, advertise, etc. are applied on a varietyof interior and exterior, vertical and horizontal surfaces. Non-limitingexamples of image graphics range from advertisements on walls or sidesof trucks, to posters that advertise the arrival of a new movie, warningsigns near the edges of stairways, and the like.

[0004] The use of thermal and piezo inkjet inks has greatly increased inrecent years with accelerated development of inexpensive and efficientinkjet printers, ink delivery systems, and the like.

[0005] Thermal inkjet hardware is commercially available from a numberof multinational companies, including without limitation,Hewlett-Packard Corporation of Palo Alto, Calif.; Corporation of SanDiego, Calif.; Xerox Corporation of Rochester, N.Y.; ColorSpanCorporation of Eden Prairie, Minn.; and Mimaki Engineering Co., Ltd. ofTokyo, Japan. The number and variety of printers change rapidly asprinter makers are constantly improving their products for consumers.Printers are made both in desk-top size and wide format size dependingon the size of the finished image graphic desired. Non-limiting examplesof popular commercial scale thermal inkjet printers are EncadCorporation's NOVAJET Pro printers and Hewlett-Packard Corporation's650C, 750C, and 2500CP printers. Non-limiting examples of popular wideformat thermal inkjet printers include Hewlett-Packard Corporation'sDesignJet printers, where the 2500CP is preferred because it has 600×600dots/inch (dpi) resolution with a drop size in the vicinity of about 20picoliters (pL).

[0006] 3M Company, of St. Paul, Minn., markets Graphic Maker Inkjetsoftware useful in converting digital images from the Internet, ClipArt,or Digital Camera sources into signals to thermal inkjet printers toprint such image graphics.

[0007] Inkjet inks are also commercially available from a number ofmultinational companies, particularly 3M Company which markets itsSeries 8551; 8552; 8553; and 8554 pigmented inkjet inks. The use of fourprocess colors: cyan, magenta, yellow, and black (generally abbreviated“CMYK”) permit the formation of as many as 256 colors or more in thedigital image.

[0008] Media for inkjet printers are also undergoing accelerateddevelopment. Because inkjet imaging techniques have become vastlypopular in commercial and consumer applications, the ability to use apersonal computer to print a color image on paper or other receptormedia has extended from dye-based inks to pigment-based inks. The mediamust accommodate that change. Pigment-based inks provide more durableimages because of the large size of colorant as compared to dyemolecules.

[0009] Inkjet printers have come into general use for wide-formatelectronic printing for applications, such as engineering andarchitectural drawings. Because of the simplicity of operation andeconomy of inkjet printers, this image process holds a superior growthpotential promise for the printing industry to produce wide format,image on demand, presentation quality graphics.

[0010] Therefore, the components of an inkjet system used for makinggraphics can be grouped into three major categories:

[0011] 1. Computer, software, printer

[0012] 2. Ink

[0013] 3. Receptor medium

[0014] The computer, software, and printer will control the size, numberand placement of the ink drops and will transport the receptor mediumthrough the printer. The ink will contain the colorant that forms theimage and carrier for that colorant. The receptor medium provides therepository that accepts and holds the ink. The quality of the inkjetimage is a function of the total system. However, the compositions andinteraction between the ink and receptor medium are most important in aninkjet system.

[0015] Image quality is what the viewing public and paying customerswill want and demand to see. From the producer of the image graphic,many other obscure demands are also placed on the inkjet media/inksystem from the print shop. Also, exposure to the environment can placeadditional demands on the media and ink (depending on the application ofthe graphic).

[0016] Current inkjet receptor media, direct coated with compositionsaccording to the disclosure contained in U.S. Pat. No. 5,747,148 (Warneret al.) and in PCT Patent Publication Nos. WO 99/07558 (Warner et al.)and WO 99/03685 (Waller et al.), are marketed by 3M Company under thebrands 3M™ Scotchcal™ Opaque Imaging Media 3657-10 and 3M™ Scotchcal™Translucent Imaging Media 3637-20, 8522, and 8544, respectively. Anotherinkjet receptor media is disclosed in coassigned PCT Patent PublicationNo. WO 97/33758 (Steelman et al.) which combines a hygroscopic layer ona hydrophilic microporous media.

[0017] Inkjet inks are typically wholly or partially water-based, suchas disclosed in U.S. Pat. No. 5,271,765. Typical receptors for theseinks are plain papers or preferably specialty inkjet receptive paperswhich are treated or coated to improve their receptor properties or thequality of the images resulting therefrom, such as disclosed in U.S.Pat. No. 5,213,873.

[0018] Many inkjet receptor compositions suitable for coating ontoplastics to make them inkjet receptive have been disclosed. Typically,these receptor layers are composed of mixtures of water-soluble polymerswhich can absorb the aqueous mixture which the inkjet ink comprises.Very common are hydrophilic layers comprising poly(vinyl pyrrolidone) orpoly(vinyl alcohol), as exemplified by U.S. Pat. Nos. 4,379,804;4,903,041; and 4,904,519. Also known are methods of crosslinkinghydrophilic polymers in the receptor layers as disclosed in U.S. Pat.Nos. 4,649,064; 5,141,797; 5,023,129; 5,208,092; and 5,212,008. Othercoating compositions contain water-absorbing particulates, such asinorganic oxides, as disclosed in U.S. Pat. Nos. 5,084,338; 5,023,129;and 5,002,825. Similar properties are found for inkjet paper receptorcoatings, which also contain particulates, such as cornstarch asdisclosed in U.S. Pat. Nos. 4,935,307 and 5,302,437.

[0019] The disadvantage that many of these types of inkjet receptormedia suffer for image graphics is that they comprise water-sensitivepolymer layers. Even if subsequently overlaminated, they still contain awater-soluble or water-swellable layer. This water-sensitive layer canbe subject over time to extraction with water and can lead to damage ofthe graphic and liftoff of the overlaminate. Additionally, some of thecommon constituents of these hydrophilic coatings contain water-solublepolymers not ideally suitable to the heat and UV exposures experiencedin exterior environments, thus limiting their exterior durability.Finally, the drying rate after printing of these materials appears slowsince until dry, the coating is plasticized or even partially dissolvedby the ink solvents (mainly water) so that the image can be easilydamaged and can be tacky before it is dry.

[0020] In recent years, increasing interest has been shown inmicroporous films as inkjet receptors to address some or all of theabove disadvantages. Both Warner et al. and Waller et al. publicationsand Steelman et al. application, identified above, disclose microporousfilms to advantage. If the film is absorbent to the ink, after printingthe ink absorbs into the film itself into the pores by capillary actionand feels dry very quickly because the ink is away from the surface ofthe printed graphic. The film need not necessarily contain water-solubleor water-swellable polymers, so potentially could be heat and UVresistant and need not be subject to water damage.

[0021] Porous films are not necessarily receptive to water-based inkjetif the material is inherently hydrophobic and methods of making themhydrophilic have been exemplified, for example, by PCT PatentPublication No. WO 92/07899.

[0022] Other films are inherently aqueous ink absorptive because of thefilm material, e.g., Teslin™ (a silica-filled polyolefin microporousfilm) available from PPG Industries and of the type exemplified in U.S.Pat. No. 4,861,644. Possible issues with this type of material are thatif used with dye-based inks image density can be low depending on howmuch of the colorant remains inside the pores after drying. One way ofavoiding this is to fuse the film following printing as exemplified inPCT Patent Publication No. WO 92/07899.

[0023] Other methods are to coat the microporous film with a receptorlayer as disclosed in PCT Patent Publication No. WO 97/33758 (Steelmanet al.) and U.S. Pat. No. 5,605,750.

[0024] As stated above, the relationship between the ink and the mediais key to image graphic quality. With printers now reaching 1400×720 dpiprecision, inkjet drop size is smaller than in the past. As statedpreviously, a typical drop size for this dpi precision, is about 20picoliters, which is a fraction of the size of prior drop sizes of 140picoliters used in wide format inkjet printers, most notably andcommonly Encad™ NOVAJET III, IV, and Pro models. Some printer makers arestriving for even smaller drop sizes, while other printer makers arecontent with the larger drop sizes for large format graphics. Withpigmented inkjet inks, drop size determines the quantity of pigmentparticles that reside in each drop and are to be directed to apredetermined area of media.

[0025] When the inkjet ink drop contacts the receptor medium, acombination of two things occurs. The inkjet drop diffuses verticallyinto the medium and diffuses horizontally along the receptor surface,with a resulting spread of the dot.

[0026] However, with pigment-based inkjet inks of the right particlesize and if used with a film of the right pore-size, some filtration ofthe colorant is possible at the surface of the film resulting in a gooddensity and color saturation. However, images can still be very poor ifdot-gain is low due to “banding phenomena” where insufficient inkremains to generate the appropriate halftone image. If dot-size is toosmall, then errors due to media advancement or failed printhead nozzlescan cause banding. This problem would not be seen with larger drop sizeprinters because larger dots could cover up prior printing errors.However, if dots are too large, then edge acuity is lost. Edge acuity isa reason for increased dpi image precision. Ability to control dotdiameter is therefore an important property in an inkjet receptormedium.

[0027] U.S. Pat. No. 5,605,750 exemplifies a pseudo-boehmite coatingapplied to the silica-filled microporous film, such as Teslin™. Thecoating contains alumina particles of pseudo-boehmite of pore radius 10to 80 Å. Also disclosed is an additional protective layer ofhydroxypropylmethyl cellulose.

[0028] Several problems exist using receptor coatings mentioned above.The rate of ink absorption is, at most for a water-swellable coating,8-10 ml/sec/M²; this is slow when compared to the rate of ink dropapplication. Secondly, the volumes of ink applied by many popular wideformat inkjet printers at 140 pL/drop (HP 2500: 20 pL/drop but 160pL/dot) can create problems, such as “feathering”, “demixing”, andcoalescence of the ink.

[0029] Because most of the printers in the office of today usewater-based inks, when those printers and inks are used on conventionalink jet films, a lot of ink must be laid down to give suitable imagedensity for transmitted images. When the ink is laid down rapidly onknown films, such as those identified above, the ink tends to sufferfrom uncontrolled coalescence, or uneven gathering of the ink drops,resulting in streaking, banding and blotching. In order to avoidcoalescence and give acceptable image quality, printers use a“transparency” mode which delivers the ink slowly over multiple passes.This results in much slower overall print speed and is a major source ofdissatisfaction with making overhead transparencies on ink jet printers.

[0030] Coassigned PCT Patent Publication No. WO 99/55537 (Ylitalo etal.) “Microembossed Receptor Media”, discloses the use of microembossedfilms for receiving and displaying images delivered by ink jet printersof various kinds, including those using water-based inks, with patternswith cavity size in the range of 20-1000 pL. This range was chosen toencompass the range of ink volumes of known printers, so that the numberof cavities per area, or cavity density, was equal to or greater thanthe resolution or dots/inch (“dpi”) of the printer.

SUMMARY OF INVENTION

[0031] Surprisingly, this invention provides excellent transparencyprinting results, achieved with cavity densities significantly below thedpi of the printer. Further, this invention has determined that thetransparency of the microembossed transparent ink jet receptor is verysensitive to the geometry of the pattern and the fidelity ofreplication, so that the desirable range of cavity size and density issignificantly different from U.S. patent application Ser. No. 09/713,610(Ylitalo et al.), also PCT Patent Publication No. WO 99/55537, thedisclosure of which is incorporated herein by reference.

[0032] There are two factors which are especially important for thisunexpected invention:

[0033] (1) overall transparency on an overhead projector; and

[0034] (2) quality of the image printed on the receptor.

[0035] Because of the optics of an overhead projector, anything in theoptical path from light source to projection screen which causes lightto miss the aperture of the collector head lens will cause less light toreach the projection screen. The collector head lens has a relativelynarrow acceptance angle, since it is designed to collect light that isnearly collimated by the fresnel lens in the projector stage. Thus, if atransparency film has a microembossed surface that refracts, diffractsor diffuses too much light, the projected image intensity is reduced,and the image can appear dark or gray. The Visual Systems Division (VSD)of 3M Company of Austin, Tex., has found that Gardner Haze can be a goodmeasure of the ability of a transparency film to reduce the lightgetting through the collector head lens. Gardner Haze is measured forall examples using a Gardner Hazemeter from BYK-Gardner Company(Columbia, Md. and D-82534 Geretsried, Germany), using ASTM D1003-97“Standard Test Method for Haze and Luminous Transmittance of TransparentPlastics”, the disclosure of which is incorporated herein by reference.Typical existing transparency films have Gardner Haze values of up to 15percent.

[0036] This invention has utility for the production of image graphicsusing inkjet printers onto a transparency for use with overheadprojection equipment commonly used in the office meeting room oruniversity lecture hall or for other light transmission uses, such asbacklit commercial signage or image graphics of decorative effect. Thisinvention unexpectedly solves such common inkjet printing problems asfeathering, banding, and mudcracking in inkjet printing systems bycontrolling how an inkjet drop contacts and dries on an inkjet receptormedium while also solving the problem of minimizing Gardner Haze asdiscussed above.

[0037] One aspect of the present invention is the use of microembossedsurfaces which can give good to excellent results with desktop and largeformat ink jet printing of image graphics for transmission of lightthrough the image graphic.

[0038] One aspect of the invention is an optically transmissive receptormedium comprising a sheet having a microembossed surface comprisingcavities as one major surface thereof, wherein the sheet is nonporous,wherein each cavity of the receptor medium has a microembossed capacityof about 1100 pL to about 5000 pL, desirably greater than about 1200 pLand desirably less than about 5000 pL

[0039] “Random” means one or more features of the microembossed elementsare intentionally and/or systematically varied in a non-regular manner.Examples of features that are intentionally and/or systematically variedin a non-regular manner are pitch, peak-to-valley distance, depth,height, wall angle, post diameter, edge radius, and the like.“Microembossed element” means a recognizable geometric shape that eitherprotrudes or is depressed. “Combination” patterns may, for example,comprise patterns that are random over an area having a minimum radiusof ten element widths from any point, but these random patterns can bereproduced over larger distances within the overall pattern.

[0040] “Inverse pattern” means the resulting pattern produced from asheet or solidifying liquid material contacts and conforms to a mold.

[0041] “Nonporous” means that the sheet is not substantially porous toliquids nor does it have a reticulated outer surface before the imagingsurface is microembossed.

[0042] A “microembossed” surface has a topography wherein the averagemicroembossed element pitch, that is, center to center distance betweennearest elements, is from about 1 micrometers to about 1000 micrometersand the average peak to valley distances of individual features is fromabout 1 micrometers to about 100 micrometers.

[0043] “Microembossing” means embossing a surface and making it amicroembossed surface, or causing a microembossed surface to be formedfrom a liquid which is solidified during the microembossing process.

[0044] Preferably, the receptor medium is an inkjet receptor medium.

[0045] Preferably, the microembossed imaging surface comprises cavitiesenclosed by walls, packed closely together, and with cavity volumecommensurate with at least 100 percent ink from the targeted printer.

[0046] Another aspect of the present invention is an imaged inkjetreceptor medium comprising a sheet having a microembossed image surfacecomprising cavities and particles of pigment or dye dried on themicroembossed image surface.

[0047] Another aspect of the invention is a method of making an inkjetreceptor medium, comprising the steps of: (a) selecting an embossingmold with a molding surface having a microembossed topography; and (b)contacting the molding surface of the mold against a polymeric sheet toform a microembossed surface on the sheet which is the inverse of themicroembossed topography.

[0048] Another aspect of the invention is a method of making an inkjetreceptor medium, comprising the steps of: (a) selecting an embossingmold with a molding surface having a microembossed topography; and (b)extruding a polymer over the molding surface of the mold to form apolymeric sheet having a microembossed surface on the sheet which is theinverse of the microembossed topography.

[0049] Another aspect of the invention is a method of making an inkjetreceptor medium comprising the steps of: (a) selecting a microembossingmold with a molding surface having a microembossed topography; (b)contacting a fluid with the molding surface; and (c) solidifying thefluid to form a sheet having a microembossed surface topography which isthe inverse of the molding surface, wherein the microembossed surfacetopography comprises cavities each having a volume of from about 1100 pLto about 5000 pL. Preferably, the fluid is a radiation curable fluid andthe fluid is solidified by exposing the fluid to actinic radiation.

[0050] A feature of the invention is a microembossed topography thatminimizes Gardner Haze to permit excellent transmission of light andfidelity of color of the image graphic created by the pigment or dye.

[0051] An advantage of the invention is the minimization of commoninkjet printing problems, such as banding, feathering, bleeding,coalescence, and mudcracking, by altering the receiving surface of theinkjet receptor medium rather than altering the formulation of theinkjet inks.

[0052] Another advantage of the invention is the ease by which amicroembossed image surface can be formed.

[0053] Another advantage of the present invention is the protection ofthe inkjet image from abrasion at the surface of the inkjet receptormedium because the colored entities forming the image reside withincavities of the topography of the microembossed image surface. As such,the medium of the present invention provides abrasion resistance, smearresistance, and prevention of feathering or bleeding of the image.

[0054] Another advantage of the invention is the usefulness of themicroembossed image surface with organic solvent-based, water-based,phase change, or radiation polymerizable inks. The inks can furthercomprise either dye or pigment based colorants.

[0055] The embodiments of the invention that follow will identify otherfeatures and advantages.

BRIEF DESCRIPTION OF DRAWINGS

[0056]FIG. 1 is an illustrative cross-sectional view of an envisionedsequence of inkjet drop deposition, drying, and final appearance usingrandom cavities.

[0057] FIGS. 2-7 show various digital images of controls and media ofthe present invention as imaged.

EMBODIMENTS OF INVENTION

[0058] Microembossed Image Surface

[0059]FIG. 1 illustrates the premise of the present invention: an inkjetreceptor medium 10 that can be constructed to have a microembossed imagesurface 12 of multiple cavities 14 for receiving and protecting pigmentparticles contained in an inkjet ink and multiple peaks 16.

[0060] At the left side of FIG. 1, one sees an inkjet drop 20, typicallyranging in size from about 10 pL to about 150 pL, and preferably fromabout 20 pL to about 140 pL, approaching microembossed image surface 12.

[0061] In the middle of FIG. 1, one sees an inkjet drop 30 within onecavity 14 as drop 30 begins to dry, cure, or otherwise gather, dependingon the nature of the inkjet ink formulation.

[0062] On the right of FIG. 1, one sees an inkjet drop 40 that has driedand resides within a cavity 14 such that it is protected from abrasionfrom items contacting the multiplicity of peaks 16 that, on amacroscopic level, constitute the outermost surface of medium 10.

[0063]FIG. 1 also illustrates an important consideration of theinvention: more than one drop of ink is destined to reside in a singlecavity, because mixing of the colors: cyan, yellow, and magenta areneeded to create the infinite number of colors now demanded in inkjetprinting.

[0064] Polymeric Film

[0065] The polymeric sheet used in the inkjet medium can be made fromany polymer capable of being microembossed in the manner of the presentinvention. The sheet can be a solid film. The sheet should betransparent or translucent, depending on desired usage. The sheet can beclear or tinted, depending on desired usage. The sheet should beoptically transmissive.

[0066] Non-limiting examples of polymeric films include thermoplastics,such as polyolefins, poly(vinyl chloride), copolymers of ethylene withvinyl acetate or vinyl alcohol, polycarbonate, norbornene copolymers,fluorinated thermoplastics, such as copolymers and terpolymers ofhexafluoropropylene and surface modified versions thereof, poly(ethyleneterephthalate) and copolymers thereof, polyurethanes, polyimides,acrylics, and filled versions of the above using fillers, such assilicates, aluminates, feldspar, talc, calcium carbonate, titaniumdioxide, and the like. Also useful in the application are coextrudedfilms and laminated films made from the materials listed above.

[0067] More specifically, transparent or transmissive polyolefins can beethylene homopolymers or copolymers, such as “ENGAGE” brandethylene-octene copolymer commercially available from Dow ChemicalCompany, Midland, Mich. Other specifically useful films include LEXANpolycarbonate from General Electric Plastics of Pittsfield, Mass.;ZEONEX polymer from B. F. Goodrich of Richfield, Ohio; THV-500 polymerfrom Dyneon LLC of Oakdale, Minn.; plasticized poly(vinyl chloride),poly(ethylene terephthalate) copolymer EASTAR 6763 from Eastman,AFFINITY PL 1845 from Dow Chemical Company, and SURLYN methacrylic acidcopolymers from DuPont.

[0068] Properties of polymeric sheets of the present invention can beaugmented with outer coatings that improve control of the inkreceptivity of the microembossed image surface 12 of the ink receptormedium 10. As stated in the Background of the Invention above, anynumber of coatings are known to those skilled in the art. It is possibleto employ any of these coatings in combination with the microembossedimage surface of the present invention.

[0069] Preferably, one can employ a fluid management system as disclosedin PCT Patent Publication No. WO 99/03685 and its copending, coassignedU.S. patent application Ser. No. 08/892,902 (Waller et al.), thedisclosure of which is incorporated herein by reference. Briefly, avariety of surfactants or polymers can be chosen to provide particularlysuitable surfaces for the particular fluid components of the pigmentedinkjet inks. Surfactants can be cationic, anionic, nonionic, orzwitterionic. Many of each type of surfactant are widely available toone skilled in the art. Accordingly, any surfactant or combination ofsurfactants or polymer(s) that will render said substrate hydrophiliccould be employed.

[0070] These surfactants can be imbibed into recessed surfaces of themicroembossed substrate. Various types of surfactants have been used inthe coating systems. These may include, but are not limited to,fluorochemical, silicon, and hydrocarbon-based ones wherein the saidsurfactants may be cationic, anionic, or nonionic

[0071] Various types of non-ionic surfactants can be used, including butnot limited to: Dupont's ZONYL fluorocarbons (for example, ZONYL FSO);BASF's (PLURONIC) block copolymers of ethylene and propylene oxide to anethylene glycol base; ICI's (TWEEN) polyoxyethylene sorbitan fatty acidesters; Rohm and Haas's (TRITON X series) octylphenoxy polyethoxyethanol; Air Products and Chemicals, Inc. (SURFYNOL) tetramethyldecynediol; and Union Carbide's SILWET L-7614 and L-7607 siliconsurfactants, and the like, known to those skilled in the art.

[0072] Various types of hydrocarbon-based anionic surfactants can alsobe used, including but not limited to: American Cyanamid's (Aerosol OT)surfactants like dioctylsulfosuccinate-Na-salt ordialkylsulfosuccinate-Na-salt.

[0073] Various types of cationic surfactants can also be used, includingbut not limited to: benzalkonium chloride, a typical quaternary ammoniumsalt.

[0074] Other coating materials may be used which are intended to improvethe appearance or durability of the microembossed and printed substrate.Many examples of inkjet receptor coatings may be found in the patentliterature, for example, boehmite alumina based coatings, silica basedcoatings, and the like should not be considered outside the scope of theinvention. If the targeted printer prints aqueous dye inks, then asuitable mordant may be coated onto the microembossed surface in orderto demobilize or “fix” the dyes. Mordants which may be used generallyconsist of, but are not limited to, those found in patents such as U.S.Pat. Nos. 4,500,631; 5,342,688; 5,354,813; 5,589,269; and 5,712,027.Various blends of these materials with other coating materials listedherein are also within the scope of the invention.

[0075] Additionally, directly affecting the substrate by means generallyknown in the art may be employed in the context of this invention. Forexample, corona treated poly(olefins) or surface dehydrochlorinatedpoly(vinyl chloride) could be microembossed and used as a printablesubstrate. Otherwise, these and other polymers could be microembossedand then corona treated to make them more suitable as printablesubstrates.

[0076] Optional Adhesive Layer and Optional Release Liner

[0077] The receptor medium 10 optionally has an adhesive layer on themajor surface of the sheet opposite microembossed image surface 12 thatis also optionally but preferably protected by a release liner. Afterimaging, the receptor medium 10 can be adhered to a horizontal orvertical, interior or exterior surface to warn, educate, entertain,advertise, etc.

[0078] The choice of adhesive and release liner depends on usage desiredfor the image graphic. Optically transmissive adhesives are preferred.

[0079] Pressure-sensitive adhesives can be any conventionalpressure-sensitive adhesives that adheres to both the polymer sheet andto the surface of the item upon which the inkjet receptor medium havingthe permanent, precise image is destined to be placed.Pressure-sensitive adhesives are generally described in Satas, Ed.,Handbook of Pressure Sensitive Adhesives, 2nd Ed. (Von Nostrand Reinhold1989), the disclosure of which is incorporated herein by reference.Pressure-sensitive adhesives are commercially available from a number ofsources. Particularly preferred are acrylate pressure-sensitiveadhesives commercially available from 3M Company and generally describedin U.S. Pat. Nos. 5,141,790; 4,605,592; 5,045,386; and 5,229,207, andEPO Patent Publication No. EP 0 570 515 B1 (Steelman et al.).

[0080] Release liners are also well known and commercially availablefrom a number of sources. Non-limiting examples of release linersinclude silicone coated kraft paper, silicone coated polyethylene coatedpaper, silicone coated or non-coated polymeric materials, such aspolyethylene or polypropylene, as well as the aforementioned basematerials coated with polymeric release agents, such as silicone urea,urethanes, and long chain alkyl acrylates, such as defined in U.S. Pat.Nos. 3,957,724; 4,567,073; 4,313,988; 3,997,702; 4,614,667; 5,202,190;and 5,290,615; the disclosures of which are incorporated herein byreference and those liners commercially available as POLYSLIK brandliners from Rexam Release of Oakbrook, Ill., and EXHERE brand linersfrom P. H. Glatfelter Company of Spring Grove, Pa.

[0081] Method of Forming Microembossed Image Surface

[0082] The microembossed image surface can be made from any contactingtechnique, such as casting, coating, or compressing techniques. Moreparticularly, microembossing can be achieved by at least any of: (1)casting a molten thermoplastic using a tool having a microembossedpattern; (2) coating of a fluid onto a tool having that microembossedpattern, solidifying the fluid, and removing the resulting microembossedsolid; or (3) passing a thermoplastic film through a nip roll tocompress against a tool having that microembossed pattern. Desiredembossing topography can be formed in tools via any of a number oftechniques well known to those skilled in the art, selected depending inpart upon the tool material and features of the desired topography.illustrative techniques include etching (for example, via chemicaletching, mechanical etching, or other ablative means, such as laserablation or reactive ion etching, etc.), photolithography,stereolithography, micromachining, knurling (for example, cuttingknurling or acid enhanced knurling), scoring or cutting, etc.

[0083] Alternative methods of forming the microembossed image surfaceinclude thermoplastic extrusion, curable fluid coating methods, andembossing thermoplastic layers, which can also be cured.

[0084] A preferred embossing tooling can be made by casting a two-partcurable silicone material over a master mold which has the same patternas desired for the microembossed image surface 12 of the inkjet receptormedium 10. The silicone mold therefore has the inverse image(cavity-forming geometry protruding). This mold can then be used in ahot press or in actual extrusion or casting operations. Extrusionembossing is accomplished by passing the mold through the nip to makemicroembossed sections on the extruded film. Another preferred tool forextrusion embossing is a metal casting roll which itself carries thenegative of the pattern which is to be microembossed on thethermoplastic sheet.

[0085] Compressing Method

[0086] This method uses a hot press familiar to those skilled in the artof compression molding.

[0087] The pressure exerted in the press typically ranges from about4.1×10⁴ kPa to about 1.38×10⁵ kPa and preferably from about 6.9×10⁴ kPato about 1.0×10⁵ kPa.

[0088] The temperature of the press at the mold surface typically rangesfrom about 100° C. to about 200° C. and preferably from about 110° C. toabout 150° C.

[0089] The dwell time of pressure and temperature in the press typicallyranges from about 1 minute to about 5 minutes. The pressure, temperatureand dwell time used depend primarily on the particular material beingmicroembossed, as is well known to those skilled in the art. The processconditions should be sufficient to cause the material to flow andfaithfully take the shape of the surface of the tool being used. Anygenerally available commercial hot press may be used, such as WabashModel 20-122TM2WCB press from Wabash MPI of Wabash, Ind.

[0090] Extrusion Method

[0091] A typical extrusion process for the present invention involvespassing an extruded substrate through a nip created by a chilled rolland a casting roll having a surface having a pattern inverse of desiredmicroembossed image surface, with the two rolls rotating in oppositedirections. A flexible sheet or belt comprising the tool may also beused and put through the nip simultaneously with the melt. Single screwor twin screw extruders can be used. Conditions are chosen to meet thegeneral requirements which are understood to the skilled artisan.Representative but non-limiting conditions are outlined below.

[0092] The temperature profile in the extruder can range from 100° C. to250° C. depending on the melt characteristics of the resin.

[0093] The temperature at the die ranges from 150° C. to 230° C.depending on the melt strength of the resin.

[0094] The force exerted in the nip can range from about 6 kN/m to about150 kN/m and preferably from about 10 kN/m to about 100 kN/m.

[0095] The temperature of the nip roll can range from about 5° C. toabout 150° C. and preferably from about 10° C. to about 100° C., and thetemperature of the cast roll can range from about 25° C. to about 100°C. and preferably about 40° C. to about 60° C.

[0096] The speed of movement through the nip typically ranges from about0.25 m/min to about 10 m/min and preferably as fast as conditions allow.

[0097] Non-limiting examples of equipment useful for this extrusionmethod include single screw extruders, such as a 1¼ inch Killion(Killion Extruders, Inc. of Cedar Grove, N.J.) equipped with a gearpump, such as a Zenith gear pump to control flow rate, co-rotating twinscrew extruders, such as a 25 mm Berstorff (Berstorff Corporation ofCharlotte, N.C.) and counter-rotating twin screw extruders, such as a 30mm Leistritz (American Leistritz Extruder Corporation of Somerville,N.J.). Flow rate in the twin screw extruder can be controlled usingweight loss feeders, such as a K-tron (K-tron America of Pittman, N.J.)to feed the raw material into the extruder. A film die with adjustableslot is used to form a uniform film out of the extruder.

[0098] Casting Method

[0099] Embodiments of the optically transmissive microembossed receptormedia may also be made using a casting process. A typical castingprocess comprises the steps of providing a tool having a molding surfacehaving a suitable pattern inverse of desired microembossed imagesurface; applying a volume of a flowable resin composition to themolding surface; contacting the resin composition with a first majorsurface of a film; minimizing excess resin composition between the filmand molding surface; curing the resin composition to form a sheetingcomprising the microembossed cavities bonded to the film; and removingthe sheeting from the tool. Further details of the casting method aredescribed in U.S. Pat. Nos. 5,183,597 and 5,304,223, incorporated hereinby reference for the casting process, and PCT Patent Publication No. WO95/11464.

[0100] A wide variety of radiation curable materials are suitable foruse in the above method for making the microembossed receptor media ofthe invention. Examples of such materials are described in U.S. Pat.Nos. 4,576,850 and 4,582,885, both incorporated herein by reference forsaid materials. The combination of monomers, oligomers and initiators inorder to obtain particular combinations of physical and chemicalproperties is known to those skilled in the art. Commercial suppliers ofsuch materials include Henkel (Amber, Pa.), Sartomer (Exton, Pa.), UCB(Smyrna, Ga.), and Ciba-Geigy (Hawthorne, N.Y.).

[0101] Usefulness of the Invention

[0102] Inkjet receptor media of the present invention can be employed inany environment where inkjet images are desired to be precise, stable,rapid drying, and abrasion resistant.

[0103] Moreover, these inkjet receptor media are optically transmissive.One measure of such optical transmission is Gardner Haze as identifiedabove. For the inkjet receptor media of the present invention, theGardner Haze, measured in Percentage Haze, ranges from about 0 percentto about 40 percent and preferably from about 0 percent to about 20percent. At these values, media of the present invention are useful foroptical transparent or translucent applications. Non-limiting examplesof such uses include overhead transparencies, backlit signage, labelstock, security cards, and the like.

[0104] Inkjet receptor media of the present invention can accept avariety of inkjet ink formulations to produce rapid drying and preciseinkjet images. The topography of the microembossed image surface of theinkjet receptor medium can be varied for optimum results, depending onseveral factors, such as: ink droplet volume; ink liquid carriercomposition; ink type (pigment or blend of pigment and aqueous ornon-aqueous dye); and manufacturing technique (machine speed,resolution, roller configuration); etc.

[0105] The imaging surface of the present invention has been found tocontrol dot location to remain within isolated cavities 14 of surface12, yet unexpectedly remain sufficiently translucent or transparent tobe useful in optically transmissive applications.

[0106] For example, a test pattern of three overlapping circles ofprimary colors (cyan, magenta, yellow), secondary colors (red, green,blue) and tertiary color (black) inkjet ink printed onto an inkjetreceptor medium of the present invention shows the precision of colorcontrol and pigment location on the medium.

[0107] Further, because the pigment or dye particles reside beneath thenominal macroscopic surface of the inkjet receptor medium, the pigmentor dye particles are protected from abrasion that does not penetrate asdeep as the location of the particles. Incidental abrasion of thegraphic during graphic handling after printing is minimized.

[0108] The possibilities of image manipulation on the surface of aninkjet receptor medium, created by the topography of the image surfaceof that medium, are myriad to those skilled in the art, because the samepattern need not cover the entire surface of the medium. For example,different patterns could be employed, stepwise, in gradation, orrandomly across an area of inkjet receptor medium, in order to createstructured or unstructured appearances for the images printed thereonwhile providing optical transmissivity nonetheless.

[0109] For example, one skilled in the art could use either regularmicroembossed patterns as disclosed in copending, coassigned, U.S.patent application Ser. No. 09/713,610 (Ylitalo et al.), also PCT PatentPublication No. WO 99/55537, or random microembossed patterns asdisclosed in copending, coassigned, U.S. patent application Ser. No.09/583,295, filed May 31, 2000, also PCT Patent Publication No. WO00/73082, for the large feature patterns of the present invention. Bothapplications are incorporated herein by reference. Moreover, one coulduse a multilayered microembossed pattern in which the cavity walls andfloors are made of substantially different materials, in order to managecoalescence of ink on cavity floors of media of the present invention.

[0110] Further, as the skill of inkjet printing increases, both in termsof ink drop size and in terms of inkjet placement, it could becomepossible that the half tone printing pattern will be so refined as toalign the printing pattern of the ink, drop by drop, with themicroembossed pattern on the medium, cavity by cavity. That would permitfull justification of the printing process resembling the imagedisplayed on a digital color monitor.

[0111] Another benefit of the media of the present invention is thecontrol of the dry time of the ink drop in each cavity. Drying can bemeasured as the time required before the image becomes tack free or doesnot smear when lightly rubbed. The use of isolated cavities to minimizemigration of color during drying is an advantage in the receptor mediumof the invention.

[0112] The formation of precise inkjet images is provided by a varietyof commercially available printers. Non-limiting examples includethermal inkjet printers, such as DeskJet brand, PaintJet brand,Deskwriter brand, DesignJet brand, and other printers commerciallyavailable from Hewlett-Packard Corporation. Also included are piezo typeinkjet printers, such as those from Seiko-Epson, Raster Graphics, andXerox, spray jet printers and continuous inkjet printers. Any of thesecommercially available printers introduces the ink in a jet spray of aspecific image into the medium of the present invention. Drying is muchmore rapid under the present invention than if the imaging layer were tobe applied to a similar non-microembossed media.

[0113] The media of the present invention can be used with a variety ofinkjet inks obtainable from a variety of commercial sources. It shouldbe understood that each of these inks has a different formulation, evenfor different colors within the same ink family. Non-limiting sourcesinclude 3M Company, Encad Corporation, Hewlett-Packard Corporation,NuKote, and the like. These inks are preferably designed to work withthe inkjet printers described immediately above and in the backgroundsection above, although the specifications of the printers and the inkswill have to be reviewed for appropriate drop volumes and dpi in orderto further refine the usefulness of the present invention.

[0114] Media of the present invention can also be employed with otherjettable materials, that is, those materials capable of passing throughan inkjet printing head. Non-limiting examples of jettable materialsinclude adhesives, biological fluids, chemical assay reagents,pharmaceuticals, particulate dispersions, waxes, and combinationsthereof.

[0115] Media of the present invention can also be employed withnon-jettable materials so long as an inkjet printing head is not neededto deposit the material on the microembossed surface. For example, U.S.Pat. No. 5,658,802 (Hayes et al.) discloses printed arrays for DNA,immunoassay reagents or the like using arrays of electromechanicaldispensers to form extremely small drops of fluid and locate themprecisely on substrate surfaces in miniature arrays.

[0116] The following examples further disclose embodiments of theinvention.

General Information

[0117] Topography of both microembossed and smooth surfaces wereexamined by interferometry using an interferometric microscope, such asWyko Roughness/Step Tester available from the Veeco Instruments ofPlainview, N.Y., or alternatively were examined by scanning electronmicroscopy or by optical microscopy where equipped for depth measurement(z-axis micrometer).

[0118] Compression Molding can be done in a number of ways. One skilledin the art will recognize the utility of various methods used. Mostcommonly, a metal tool (surface of nickel or chrome) impressed with thepattern in question, was used directly in compression molding against athermoplastic material at sufficient temperature, pressure, and time toreplicate the inverse of the pattern onto the thermoplastic.Alternatively, metal tooling can be used as a mold against which to casta curable silicone rubber which can subsequently be used in compressionmolding. Finally, microembossed thermoplastics can also be used astemplates against which curable silicone rubber is cast. Polyimide inparticular is useful for both silicone casting and compression moldingof lower melting thermoplastics.

[0119] Desktop printers: Hewlett-Packard Corporation HP 800 seriesprinters (855, 870, 892): dye inks with pigmented black, drop sizearound 20 pL, used in “plain paper” printing mode at “normal” printingspeed or “transparency” mode at “normal” speed. HP 2000: dye inks withpigmented black, drop size around 20 pL, used in “plain paper” mode ateither “Econofast” or “normal” speed, or “transparency” mode at “normal”or “presentation” speed, or “rapid dry transparency” mode at“presentation” speed.

[0120] UV Curable Inks: Trident BASIC PIXELJET Evaluation Kit#064-1010-01 at 172×172 or 344×344 dpi.

[0121] Test patterns: Desktop prints were made using either “TESTPATTERN 1”, a standard 3M Company print test which comprises colorblocks with thin lines of other colors intersecting them, or “TESTPATTERN 2”, a test pattern which writes black pigmented text over colorblocks.

EXAMPLES Example 1 Generation of Substrates and Gardner Haze

[0122] In this example, large features are shown to provide acceptableGardner Haze in an image projected by an overhead projector. GardnerHaze is measured for all examples using a Gardner Hazemeter fromBYK-Gardner Company (Columbia, Md. and D-82534 Geretsried, Germany),using ASTM D1003-97 “Standard Test Method for Haze and LuminousTransmittance of Transparent Plastics”, the disclosure of which isincorporated herein by reference.

[0123] Four topographies were generated on polyimide film (DuPont ofWilmington, Del.) by laser ablation. All patterns comprised inverseimages of closely packed square cavities having a height (H); wallthickness at the wall top (B); an angle (A) of wall to a planeperpendicular to the plane of the sheet; and pitch (P) orcenter-to-center distance between adjoining cavities. The polyimide filmwas used in compression molding of polycarbonate film (General Electric,Fairfield, Conn.) such that replication is essentially complete viainterferometry. The dimensions of the cavities formed in thepolycarbonate film are outlined in Table 1. Also shown is the calculatedpercent non-planar area, or % NPA, of each topography. Generally, the %NPA of the invention is 10 percent or less. The % NPA comprises thetheoretical non-parallel, non-perpendicular area of the sheet when thesheet is situated horizontally. Finally, Table 1 contains the measuredvalue for Gardner Haze. TABLE 1 Pattern Name P (μm) A (°) B (μm) H (μm)% NPA Haze 200 LPI 125 7 16 25 12 25  100 LPI 250 7 16 25 6.6 15.3 75LPI 338.7 14.5 4 25 7.3 11.3 50 LPI 508 14.5 3 25 5.4  7.5 none na na na0 0 <1  

[0124] As the size of the cavities increases, both the theoretical % NPAand actual haze decrease. The “200 LPI” pattern gives haze which isconsidered aesthetically too high for overhead projector transparencyapplications, while 100, 75, and 50 LPI provide acceptable haze.

Example 2 Effect of Mastering Method on Haze Performance

[0125] The amount of haze resulting from the light scattered from themicroembossed receptor surface is minimized by controlling certainaspects of the design, for example, by requiring steep wall angles andclose to zero radius (sharp) corners. The machining method chosen tofabricate a microembossed surface can ultimately have an effect ontransparency film performance parameters, such as haze. The minimumcorner radius achievable using one machining method may be much largerthan that attainable using another. If a given mastering techniquecannot produce corners with radii less than a few micrometers, there islikely to be a significant amount of light refracted from these cornersin undesired directions. The cumulative effect of this extraneousrefracted light over a relatively large area of microembossed surfacecould contribute to an increased percent haze over that from anotherfilm that is identical to the first in all respects except havingfeatures with much sharper corners. There are other subtle differencesin surface structure related to mastering method that could also affecthaze, for example, differences in flatness and surface finish of theplanar areas that are parallel to the back of the film could producedifferent types and amounts of scattering that might influence haze.

[0126] The correlation in haze performance between microembossed filmsmade using two commonly used machining techniques was measured. Thefirst mastering technique, laser ablation, is described in PCT PatentPublication No. WO 96/33839, the disclosure of which is incorporatedherein by reference. A second mastering technique, precision diamondmachining is described in “Manufacturers Turn Precision Optics withDiamond”, by E. Ray McClure, Laser Focus World, February 1991, pp.95-105. These techniques were used to fabricate one master die eachusing the same 75 LPI closely packed square void surface structuredesign (Example 1). Magnified images of each of these were made usingscanning electron microscopy (SEM). The master that was made using laserablation had corner radii of approximately 2 micrometers, more than anorder of magnitude greater than the corner radii of the master madeusing diamond machining. Nickel molds replicated from each of the twomaster dies were used to emboss blank films of 250 micron thick clearLEXAN Polycarbonate (available from the General Electric Company,Pittsfield, Mass.). Both of the polycarbonate films were microembossedby pressing at 190° C. and 5 tons of load for 2 minutes followed byanother 2 minutes at 190° C. under 10 tons of load. The percent haze ofeach microembossed polycarbonate film was measured using a “haze meter”,such as those manufactured by the BYK-Gardner Company (Columbia, Md. andD-82534 Geretsried, Germany), using ASTM D1003-97 “Standard Test Methodfor Haze and Luminous Transmittance of Transparent Plastics”. Anunexpected result of this experiment was that the measured percent hazevalue was the same, 7.5 percent for both the microembossed film samples,independent of the mastering technique used to fabricate themicroembossed surface master die. Generally, the receptor media of theinvention have a Gardner Haze of from about 0 to about 20 with values ofabout 0 to about 10 being preferred.

Example 3 Coalescence Control in Projected Images—Hydrophobic Surface

[0127] In this experiment, we will show how coalesced inks on surfacesstill provide uniform projected images when the surface to be printedcomprises patterns of the current invention.

[0128] Transparent poly(vinyl chloride) (Scotchcal™ Translucent Film,available from 3M Company) was microembossed with the 100 LPI patternand was printed upon by an HP 890C ink jet printer in “plain paper”mode, “Econofast” speed. The result was a very uniform appearing image,compared to the blotchy image obtained with even a normal ink jetreceptor film, such as CG3460 (obtained from 3M Company) orHewlett-Packard Corporation's “Rapid-Dry” Inkjet Transparency sheets(obtained from the Hewlett-Packard Corporation). However, the image onthe microembossed film was of low density because the ink beads up inthe corners of the cavities on the low energy poly(vinyl chloride)surface. Micrographs of this example show that the ink coalesces in aregular pattern, being confined within individual cells, and thusprovides a uniform appearance when viewed as a projected image on anoverhead projector, such as the 3M Company 2150 overhead projector,available from 3M Company through its Visual Systems Division located inAustin, Tex. FIG. 2 shows a digital image of a micrograph (50×) ofExample 3. FIG. 3 shows a digital image of the projected image using a3M Company 2150 overhead projector of the micrograph (50×) of Example 3.

Example 4 Comparisons of Various PVP:Primacor Based Coatings with TopLayer; Variable Well Depths, 100 LPI Pattern

[0129] In this experiment, we will show that good dry times, imagedensity, and coalescence control can all be had by using microembossedhydrophilic coatings.

[0130] PET (polyester film from 3M Company) was coated with about 20micrometers of various blend ratios of poly(N-vinyl pyrrolidinone)(PVP-K90, obtained from ISP Corp. of Wayne, N.J.) and anethylene-acrylic acid copolymer (Primacor, Dow Chemical Company) toppedwith 6 micrometers of the colloidal alumina-methylcellulose surfactantand a cationic resin dispersion as disclosed in PCT Patent PublicationNo. WO 99/39914), the disclosure of which is incorporated herein byreference (“Ali”). The samples were microembossed with the 100 LPIpatterns via compression molding. Coating compostions and depth ofmicroembossed cavities of the 100 LPI pattern are shown in Table 2below. TABLE 2 A.) Sample Identities and Haze Sample No. Well Depth HazeIdentity 1 12-14 21-26% 70:30 PVP:Primacor, 21 mic.; micrometers Topcoat“Ali” 6 micrometers 2 20-25 18-24% 70:30 PVP:Primacor, 21 mic.;micrometers Topcoat “Ali” 6 micrometers 3 12 micrometers 23-24% 85:15PVP:Primacor, 20 mic.; Topcoat “Ali” 6 micrometers 4 25 micrometers16-18% 85:15 PVP:Primacor, 20 mic.; Topcoat “Ali” 6 micrometers 5 20micrometers 16-24% 85:15 PVP:Primacor + 15% Pycal, 22 mic.; Topcoat“Ali” 6 micrometers 6 25 micrometers 19-24% 85:15 PVP:Primacor + 15%Pycal, 22 mic.; Topcoat “Ali” 6 micrometers 7 — — CG3420, Control

[0131] These samples were then printed upon using an HP 890C printer in“plain paper” mode, “Econofast” speed, manual color adjustment with fulldark intensity and scatter halftoning with the pigmented black ink. Drytime for a 1 inch square (2.54×2.54 cm) black box is less than onesecond. The resulting densities were measured by MacBeth Densitometerand are shown below in Table 3. TABLE 3 B.) HP 890C Printer: Black BoxDensity, Plain Paper, Econofast Mode Manual Color: Full Dark Density,Yellow Status A Filter, MacBeth Densitometer Sample No. 1 2 3 4 5 6 7Density 0.75 0.59 0.66 0.56 0.60 0.54 0.62

[0132] The results showed that coalescence was well-controlled. In thefollowing tables, various printers in various print modes as shown wereused to test dry time and image density for full color images. Imagedensity was measured by Macbeth Densitometer. Dry time was measured bywaiting for either 30 or 60 seconds after the print is removed from theprinter before placing paper over the print and rolling a 5 pounds (2.26kg) roller over the paper. The reflective image density of any inktransferred to the paper was then read using a MacBeth Densitometer.These results are shown in Tables 4 and 5 below. TABLE 4 C.) HP 890CPrinter: Color and Black Densities Using Transparency Mode TEST PATTERN:2 Pattern, Transparency, Best Quality Mode; Color: Automatic ImageDensities Sample Well Cyan Magenta Yellow Red Green Blue Black No. Depth(R) (G) (B) (G, B) (R, B) (R, G) (Y) 1 12-14 mic 1.25 1.13 0.91 1.15,.85 1.01, .72 1.28, .59 1.43 2 20-25 mic 1.19 1.06 0.82 1.02, .81  .88,.68 1.17, .55 1.36 3 12 mic 1.27 1.13 0.86 1.05, .81  .95, .70 141, .601.47 4 25 mic 1.10 0.96 0.76  .92, .77  .75, .63 1.01, .52 1.26 5 20 mic1.31 1.14 0.92 1.16, .84 1.01, .71 1.41, .61 1.48 6 25 mic 1.17 1.010.79  .96, .79  .81, .66 1.06, .54 1.38 7 — 1.64 1.32 0.94 1.17, .871.11, .73 1.57, .61 1.60

[0133] TABLE 5 D.) HP 890C Printer: Drytimes. Black, Red, Green, BlueBoxes Printed in Transparency Mode, Best Quality; Color: AutomaticSample Delay Black Red Green Blue No. (Second) (Y) (G, B) (R, B) (R, G)1 60 0.01 .03, 0   0, 0 .01, 0   1 30 0.07 .03, .01 0, 0 .02, .01 2 300.08 0, 0 0, 0 0, 0 3 30 0 .09, .02 .04, 0   .04, .02 4 30 0 .03, .01 0,0 0, 0 5 30 0.01 .09, .03 .05, .01 .06, .03 6 30 0 .05, .01 0, 0 0, 0 760 0.13 .04, .01 0 0 7 30 0.19 .07, .02 .04, .00 .04, .02

[0134] Finally, the same set of tests with the same set of substrateswas carried out on the HP 2000 printer. The results of dry time analysisare shown below in Table 6. TABLE 6 E.) HP 2000C Printer: Drytimes.Black, Red, Green, Blue Boxes. Imaged in “Rapid Dry Transparency” Mode,Normal Quality; Color: Automatic Sample Black Red Green Blue No. (Y) (G,B) (R, B) (R, G) 1 0.13 .09, .17 .09, .09 .09, .04 2 0.12 .04, .07 .02,.02 .03, .01 3 0.04 .14, .22 .13, .12 .19, .09 4 0 .10, .16 .07, .06.09, .04 5 0.04 .17, .23 .16, .13 .25, .14 6 0.03 .16, .22 .16, .13 .16,.09 7 0.24 .10, .15 .08, .06 .10, .04

Example 5 Effect of Embossing on Coalescence Using very Fast PrintSpeeds—Swellable Coatings

[0135] This example shows that image defects due to non-uniformcoalescing of ink droplets on the surface of swellable coatings can beeliminated by embossing the surface with patterns of the currentinvention. These defects include beading, pooling and banding. Bandingresults from adjacent rows of droplets coalescing and contracting andnot overlapping with succeeding rows of droplets as the printheadproceeds in incremental jumps. These image defects minimize the speed atwhich ink jet films may be printed and embossing can therefore allowmuch faster print speeds.

[0136] A sheet of T120 Computer Graphics Film (3M Company, no longeravailable), consisting of a 1:1 blend by weight if polyvinylpyrrolidone,(PVPK90, available from International Specialty Products, ISP), andpolyvinylalcohol (Airvol 540, available from Air Products), coated atapproximately 1.2 g/ft2 (12.9 g/m2) was printed using an HP 890C inkjetprinter in “plain paper” mode, “Econofast” speed, “manual” coloradjustment with full dark density and “Scatter” halftoning. A 1 in²(2.54 cm×2.54 cm) black box was printed with the pigmented ink,requiring less than one second to print. The resulting image showsextensive coalescence, with large openings occurring in near lineararrays.

[0137] A second sample of the above film was subjected to compressionmolding against nickel tooling to form a 100 LPI pattern on the coated

[0138] surface. This sheet was printed in a manner identical to thatdescribed in this Example above. The digital image of the micrograph ofFIG. 6 shows the ink to be compartmentalized, with uniform openings andinked areas in all directions. As a result, the screen image is totallyuniform and free from banding, as well as any other visual defects asshown in the digital image of FIG. 7.

[0139] Coalescence using fast print speeds on swellable coatings istypically worse than above. The projected screen image and micrographare shown for commercial ink jet printer film CG3420 (available from 3MCompany), printed in a manner identical to above. Extensive coalescenceresults in a very mottled and unacceptable image on the screen as shownin FIG. 4 and FIG. 5 is a digital image of a micrograph of this sample.

Example 6

[0140] Using a Trident Basic PixelJet Evaluation Kit #064-1010-01 fromTrident International Inks of Brookfield, Conn., print tests werecarried out on microembossed media of the current invention. Pigmentedblack UV curable ink, from Sun Chemical of Fort Lee, N.J., was used tomake a test pattern consisting of large font size text. The printheadwas used to deliver 172×172 dpi at 90 pL/drop.

[0141] Poly(vinyl chloride) samples, Scotchcal™ marking film (availablefrom the 3M Company), were microembossed with polyimide tooling whichwas directly laser ablated with the inverse pattern corresponding to a100 LPI pattern at 25, 35, and 50 micrometers depth (of the well). As acontrol, flat film was also printed upon. These varying depth cavitiesin PVC were then subjected to print tests on the Trident printer. Thesmearing of the inks were then examined immediately after printing, butbefore cure, using a cotton tipped swab with hard hand pressure.

[0142] The image on the flat film smeared easily upon rubbing the print.However, all the microembossed prints were not easily smeared. At 35micrometers depth, the ink smear was almost not noticeable; at 50micrometers depth, the ink could not be smeared immediately afterprinting.

Example 7 Generating an Optically Transmissive Inkjet Receptor UsingRadiation Curable Materials

[0143] A UV curable resin was prepared by adding 5 grams of hydroxyethylacrylate (Aldrich Chemical Company, Milwaukee, Wis.), 0.15 gram of SR610(Sartomer Company, Exton, Pa.), 0.19 gram of SR9035 (Sartomer Company,Exton, Pa.), and 0.16 gram of Darocur 1173 (Ciba Specialty Chemicals,Tarrytown, N.Y.) to 10 grams of a 50/50 solution of 10 k molecularweight polyvinylpyrrolidone (Aldrich Chemical Company, andN-vinyl-2-pyrrolidone (Aldrich Chemical Company). A 75 LPI tool(Example 1) made of silicone (“SILASTIC J” two-part RTV silicone,obtained from Dow Corning Co, Midland, Mich.) was coated with the UVcurable resin and a piece of MELINEX 617 (ICI of Wilmington, Del.) waslaminated onto the resin coated tool using a hand ink roller to minimizethe coating thickness. The resin was cured by irradiation through theMELINEX using a MetalBox medium pressure mercury lamp on its highsetting at a speed of 11.3 m/min. After removing the cured resin/MELINEXfilm composite from the tool, the microembossed side was irradiated at11.3 m/min beneath the mercury lamp.

[0144] A smooth resin-coated control was also produced using aknotch-bar coater set to make a 1.5 mil thick coating. The UV curableresin was cast between a sheet of plain 5 mil PET film (3M Company) anda sheet of MELINEX 617. The resin was cured by irradiation through theMELINEX using a MetalBox medium pressure mercury lamp on its highsetting at a speed of 11.3 m/min. The plain PET was then separatedleaving the MELINEX film with a smooth resin coating.

[0145] The microembossed sample and the smooth sample were printed withcyan, magenta, yellow, red, green, blue, and black color blocks on aHewlett-Packard Corporation HP 2500 desktop printer using “HP PremiumTransparency” mode, “Best” quality, and “Automatic” color settings. Thecolor blocks looked sharp and uniform on the microembossed sample whilethey looked mottled and non-uniform on the smooth sample. The dry timewas measured as before and the results are shown in Table 7 below. TheGardner Haze of the unimaged microembossed sample was 8.2 percent asdetermined by the method described in Example 1. TABLE 7 Drytime:Reflective Print Density Measured 30 Seconds After Imaging Red GreenBlue Sample Cyan Mag Yel M Y C Y M C Black 75 LPI 0.36 0.26 0.16 0.210.2 0.18 0.14 0.22 0.34 0.06 Radiation Cured Receptor Control: 0.41 0.320.22 0.41 0.36 0.38 0.27 0.49 0.68 0.26 smooth coating

[0146] The invention is not limited to the above embodiments. The claimsfollow.

What is claimed is:
 1. A method of making a receptor medium, comprisingsteps of: (a) selecting a microembossing pattern for forming amicroembossed surface on the receptor medium, wherein the embossingpattern is selected to result in an optically transmissive receptormedium; and (b) contacting a molding surface of a mold having theselected microembossing pattern against a nonporous sheet to form themicroembossed surface on the sheet which is the inverse of themicroembossed topography of the mold surface, wherein the microembossedsurface comprises cavities, each having a volume of from about 1100 pLto about 5000 pL.
 2. The method of claim 1, wherein the contacting stepis selected from the group consisting of casting, coating, andcompressing techniques.
 3. The method of claim 1, further comprisingcontacting the microembossed sheet with a topical coating.